As a mobile phone, a digital AV device, an IC card, and the like product are improved in their functionality, it is increasingly demanded that a semiconductor chip (hereinafter referred to as “chip”) which is to be mounted be downsized and thinned, so that the chip can be integrated in a package with higher density. In order to achieve high-density integration of the chip in the package, it is necessary to thin a thickness of the chip to a range from 25 μm to 150 μm.
However, a semiconductor wafer (hereinafter referred to as “wafer”) from which the chip is produced is ground to have a thinner thickness and thereby has a weaker strength. As such, a crack is more likely to be formed in the wafer, or the wafer is more likely to be curbed. In addition, it is difficult to automatically transport the wafer having the weaker intensity due to the thin thickness. As such, it is required to manually transport the wafer, and thus, handling of the wafer becomes complex.
Accordingly, a wafer support system is developed in which a plate (so called a support plate) made of glass, rigid plastic, or the like material is stuck onto the wafer that is to be thinned, so that the strength of the wafer can be retained. This prevents formation of the crack and curbing of the wafer. Because the strength of the wafer can be maintained by the wafer support system, it is possible to automatically transport the thinned semiconductor wafer.
The support plate is stuck onto the wafer with an adhesive tape, a thermal plasticity resin, an adhesive agent, and the like. The wafer onto which the support plate has been stuck is thinned, and then, the support plate is removed from the substrate before dicing the wafer. For example, in a case where the support plate is stuck onto the wafer with the adhesive agent, the adhesive agent is dissolved so that the support plate is removed from the wafer.
Conventionally, in order to remove the support plate from the wafer by dissolving the adhesive agent, it takes some time to, for example, diffuse a solvent into the adhesive agent and dissolve the adhesive agent into the solvent. As a result, it takes long time to remove the support plate from the wafer. In order to solve such a problem, Patent literature 1 discloses a sticking method for sticking a support plate onto a wafer with an adhesive agent that allows easy removal.
Patent Literature 1 discloses an art in which workpieces are bonded to each other with an adhesive agent having a first adhesive layer and a second adhesive layer on the first adhesive layer, the first adhesive layer being formed from a first adhesive material in which thermally-dissolvable microcapsules each containing a release agent for reducing adhesibility of the first adhesive material have been dispersed and the second adhesive layer being formed from a second adhesive material in which thermally-expandable particles have been dispersed.
Patent Literature 1 teaches that the workpieces bonded to each other with the adhesive agent can be removed from each other by heating the adhesive agent so as to introduce the release agent from the microcapsules into the first adhesive layer and crack the first adhesive layer and the second adhesive layer due to a pressure by heat expansion of the thermally expandable particles. This allows separating the workpieces without leaving a residue of the adhesive agent on the workpieces.